Liver enzymes drifting down and what that usually means posts 31–60
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
Analytical imprecision: any measurement has an error margin. A small difference in consecutive tests is usually measurement noise, not a real change. Knowing the imprecision helps distinguish noise from signal.
If anyone has run this properly I would rather read that than my own guess.
For anyone finding this later: the short answer on liver enzymes drifting is that it depends on one thing, and the rest of the thread is people identifying which thing.
Where I part company with post #32, and it is a narrow parting.
Repeat before acting is standard practice for an isolated abnormal result on most analytes, and it is standard for a reason.
Liver enzyme changes during rapid weight loss are commonly reported and have several possible explanations, which is exactly why they need clinical interpretation rather than forum interpretation.
The general case is well covered; this is the awkward specific one.
Before the thread moves on from liver enzymes drifting — what is the sample size behind the claim? I am not being difficult; I have seen the same figure quoted from an n of four and from an n of four hundred.
Post #36 put the caveat in the right place and I want to underline it.
The confident answers on liver enzymes drifting and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.
Where I have landed on liver enzymes drifting, having got it wrong once in public: the direction is clear, the magnitude is not, and anyone quoting a precise magnitude has borrowed it from somewhere that did not measure it.
Repeat before acting is standard practice for an isolated abnormal result on most analytes, and it is standard for a reason.
Worth separating two things that post #38 runs together.
Where a panel includes a calculated value, that value inherits the imprecision of everything it was calculated from and is usually reported without an interval.
This follows post #41 rather than contradicting it.
Analytical imprecision: any measurement has an error margin. A small difference in consecutive tests is usually measurement noise, not a real change. Knowing the imprecision helps distinguish noise from signal.
Checked the liver enzymes drifting claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
Reporting rather than recommending, on liver enzymes drifting. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
On post #41 — agreed on the reasoning, with one qualification.
Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same.
Written from notes rather than memory, which is why the numbers are specific.
The most useful reply I ever got about liver enzymes drifting was a request to state my units. It sounds like pedantry and it has saved me twice.
Right, and stated more narrowly than I would have dared to state it.
A trend needs at least three points to be a trend. Two points are a line and a line through noise is still a line.
That holds under the stated conditions and I have stated them.
Adding the measurement that post #49 says would settle it.
Worth separating liver enzymes drifting as a question about the compound from liver enzymes drifting as a question about the documentation. They get answered by different people and only one of them is answerable here.
Post #50 describes the usual case. This is about the unusual one.
Sample handling before analysis affects several analytes, and a haemolysed sample produces predictable artefacts that a laboratory will usually comment on.
Adding the boring version of liver enzymes drifting, because the interesting version keeps getting posted and the boring one is usually right.
Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does.
The question underneath liver enzymes drifting is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
Answering the question post #54 raises rather than the one it answers.
Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same.
Post #56 is the version of this I will quote in future. One addition.
Reference intervals: constructed to contain the central 95% of a reference population, which means one in twenty healthy people falls outside one by definition. Add biological variation and analytical imprecision and the base rate of a meaningless flag is substantial.
Repeat before acting is standard practice for an isolated abnormal result on most analytes, and it is standard for a reason.
I would put this at better than even and not much better.
No notes. Posting so the count is not one.